Janet Yellen's right hand man is turning more cautious on a key decision facing the Fed

Three weeks ago, Federal Reserve Vice Chair Stanley Fischer was fairly certain the central bank would raise interest rates another two times this year. Now, he's not so sure. Neither are the markets.

Speaking on CNBC on March 28, Fischer said of raising rates a total of three times this year, meaning two more following March's increase: "That is my forecast."

But with US economic data disappointing lately, Fischer seems to backing off his prediction, even as financial markets reduced the odds of a June rate increase.

Acknowledging he was surprised about weakness in first quarter economic growth, which the Atlanta Fed currently forecasts will be just a 0.5% annual rate, Fischer said, again on CNBC, "We are dependent on what happens in the economy, and we're not tied to three."

It's not the first time the Fed would be walking back on optimistic forecasts about the economy and their ability to continue pushing borrowing costs higher. In 2016, the Fed kicked off the year talking about the prospect of four rate increases. It ended up raising the official fed funds rate just once, by a quarter percentage point, at the central bank's very last meeting of the year.